The present invention relates to thin film magnetic recording heads. In particular, the invention relates to an improved thin film magnetic head design which reduces undershoot or inter-symbol interference.
In a magnetic storage system, such as a computer disk drive, digital information is magnetically stored upon the surface of a magnetic medium such as a magnetic storage disk. The digital information is represented by selectively polarizing the magnetic field of consecutive areas across the surface of the rotating magnetic disk. When this information is read back from the storage disk, the magnetic polarization of the medium is sensed as an electrical output signal. The electrical output signal is representative of both the relative strength of the magnetization in the media, and the magnetic field pattern of the read head. The readback signal comprises a series of superimposed symbols whose existence and location are used to represent digital information. The read and write operations are performed by a magnetic read/write head which is flying over the surface of the rotating disk.
Thin film transducers sense the recorded magnetic transitions primarily as these transitions pass in front of the transducer gap. This is an isolated readback pulse. However, Thin Film Transducers sense the recorded magnetic transitions not only as these transitions pass in front of the transducer gap but also when the transitions pass the leading and trailing edges of the transducer pole faces. A single transition thus produces a small leading signal pattern commonly called leading edge undershoot, a main signal called the gap response and then a small trailing signal pattern called trailing edge undershoot.
In disc storage applications, where the transition velocity varies as a function of radial distance from disc center, the positions of these undershoots relative to main signal is not constant. This makes electronic compensation difficult. In the absence of effective compensation these undershoots reduce the signal to noise ratio and tend to degrade data recovery, thus increasing the error rate of the recording system.
Reducing the amplitude of these leading/trailing edge signals or eliminating them totally would improve signal integrity and the error rate of a data recording system.